JPS58142833A - Control method for injection molding machine - Google Patents

Abstract

PURPOSE:To eliminate variance at every each cavity, and to obtain excellent products at all times from all cavities by independently controlling changeover to injection holding pressure from injection filling at every each cavity. CONSTITUTION:When resin melted is injected and filled into a plurality of cavities 30, 31' in a die 7 from one injector, the injection filling pressure of resin is detected at every each cavity 30, 31', the positions of each nozzle chip 20, 20' corresponding to several cavities 30, 30' are controlled separately on the basis of the detection, and the openings of each nozzle gate 18, 18' are controlled separately, thus filling resin under an optimum state at every each cavity 30, 30'. Accordingly, even when there is variance in the accuracy of processing of each cavity 30, 30' and there is abnormality in each hot runner 16, 16', etc., resin can be injected and filled under the optimum state, and excellent resin shapes can be obtained without generating short shots and over-packs. The damage of the die resulting from over-packs can also be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control method for a so-called multi-piece injection molding machine that simultaneously injection molds a plurality of resin molded articles in one injection process.

Conventionally, in injection molding machines, the quality of molded products was controlled by
, resin pressure inside the mold to obtain high quality molded products,
Temperature, working oil pressure, mold distortion, etc. are detected, and if the detected value is greater than or equal to the stroke of the injection screw in the injection device, the timing of switching from injection to injection holding,
A method for automatically controlling the injection amount, etc. So-called adaptive b
However, in the conventional method, the resin pressure, etc. is detected at one point in the mold, and the injection conditions, such as the injection stroke, are comprehensively controlled by the injection device. This is effective when injection molding a single piece, such as with an injection molding machine, but it is also effective when one mold has multiple cavities and multiple molded items are simultaneously injection molded in one injection process. In the case of so-called multi-piece molding, the control performance could not be fully demonstrated.

That is, for example, when injection molding four resin molded products using a mold having four cavities, the injection pressure by the injection device (resin pressure in the cylinder) will be on line 1, as shown in Figure 4. In contrast to the control shown in FIG. Second
．． Third. The resin pressure in each of the fourth cavities differs depending on the shape of each cavity, variations in processing accuracy, etc., and the respective doses are 1. Death device 3. It changes as shown in Seal 4.

The optimal filling pressure for each cavity at this time is Pa.

Pa2+ pa, I ``a4.In such an injection process, conventionally, only the resin pressure in one point of the mold, for example the cavity to be filled last, in this case the third cavity, is detected and the filling is performed at one point in the mold. When the injection device switches from injection to injection holding based on the pressure Pa5, the injection device injects the resin in the first, second, and fourth cavities that have been filled first after the filling is completed. Due to the applied pressure, there is a risk of overpacking, causing burrs and damaging the mold.In order to prevent this overpacking phenomenon, the cavity that is filled first is When switching from injection to injection holding is performed based on the filling pressure Pa1 in the first capacity, the second, sixth and fourth
Underfilling (short cuts or sink marks) occurs for each cavity.

In addition, in the conventional control method described above, when the pressure in the third cavity is detected and the switching between injection and injection holding of the injection device is feedback-controlled, a nozzle other than the third cavity, for example, corresponding to the second cavity, is If it gets clogged,
- Appropriate control is performed on the 6th Capacity, but
The second cavity may be damaged or have sink marks, and the first and fourth cavities may be overpacked, and in more serious cases, burrs may occur, so only one out of four pieces will be good. You will not be able to obtain

In addition, if an abnormality such as a disconnection or foreign matter occurs in the hot runner or nozzle corresponding to the third cavity, the hot runner or nozzle corresponding to the third cavity should Second. All of the resin flows into the fourth cavity to form an overpack, and the amount of overpack gradually increases due to feedback control of the injection amount, which may cause damage to the mold.

The present invention was made in order to solve these conventional drawbacks, and in the injection molding method used by many priests, injection filling is carried out independently of each other for a plurality of cavities provided in a mold. By controlling the switching from to injection holding pressure, each cavity is individually filled and held under optimal conditions, eliminating variations in each cavity and ensuring that good products are always obtained from all cavities. This is what I did.

The method of the present invention is characterized by injecting and filling a plurality of molten resin into a number of cavities provided in a mold using an injection device to form a plurality of resin molded products. The resin pressure in each cavity is individually controlled by individually controlling the position of the chip and the opening degree of each nozzle gate.

Hereinafter, the present invention will be explained based on embodiments shown in the drawings.

Reference numeral 1 denotes a well-known injection device, which is equipped with a hopper 2, an injection cylinder 3, an injection screw 4, an injection nozzle 5, etc., and has a rotational drive part (not shown) for the injection screw 4 and an injection hydraulic cylinder 6 at the rear end. Equipped with

7 is a mold device, which includes a fixed platen 8, a movable platen 9 that faces the fixed platen 8 and is slidably provided by a plurality of tie rods (not shown), and a fixed metal plate attached to the fixed platen 8. Type 10
It is composed of a movable mold 11 and the like attached to a movable platen 10 in a position facing the fixed mold 9. It should be noted that the mold device 7 used has a plurality of molds having a plurality of cavities inside. In this embodiment, a mold device for four molds is illustrated, and its specific structure is shown in FIG.

In FIG. 2, 12 is a dilocate ring, 13 is a sprue bush, and 14 is a sprue. The fixed mold 10 is constructed by combining a plurality of template plates 15...
is fixed by well-known means. There are four mold holes 19*19' (only two are shown) on the surface of the fixed mold 10.
is provided.

Each mold hole 19, 19' has a sprue 14 inside the fixed mold 10.
The sprue 14 is connected to the hot runner 16, 16', nozzle 17, 17', and nozzle gate 18, 18', which are branched from the hot runner 16, 16', and nozzle gate 18, 18'. 20.2
0' is the nozzle tip, each tip is connected to nozzle 17.1
It is provided so as to be slidable in the axial direction on the mold plate 15 of the fixed mold 10 so as to face 7'lli'S.

21.21' is a hydraulic cylinder for sliding each nozzle tip 20.20', 22.22' is a link, and each link 22.22' has a bearing member provided in the template 15 in the center. 23.23' is rotatably provided via a pivot 24°24', one end is connected to the rod tip of the hydraulic cylinder 21) 21' by a connecting pin 25°25', and the operation of each hydraulic cylinder 21.21' is Accordingly, each link 22
．． 22', and the opening degree of each nozzle gate 18, 18' is varied from the minimum value 1° shown in FIG. 5a to the maximum value mu ax shown in FIG. It can be adjusted with. 21a+21b and 21'
a.

21'b is the oil chamber of each hydraulic cylinder 21.21', 21c
.

21a and 21'c e 21'a indicate ports,
26° 26' indicates a nozzle heater provided around each nozzle 17.17', and 27.27' indicates a cooling medium supply hole.

On the other hand, the movable mold 11 is constructed by combining a large number of template plates 28... and cores 29° 29' facing each of the mold holes 19119', and is fixed to the movable plate 9 by well-known means. Each core 29, 29' and each mold cavity 19, 19' form each cavity 30. ! 10' is constructed. Each core 2
9y29' are provided with pressure sensors 31 and 31', respectively, and the tips of each sensor are made to face into the cavities 30*30' so that the pressure in each cavity 30#30' can be detected individually.

Each pressure sensor 31131' may be built into the ejector pin, or may be provided separately from the ejector pin. 5
2 is an ejector plate, and 35 is a spacer block.

Next, the control circuit will be explained.

In Figure 1, Toly PO2, TO5+ P
O4 is a converter for converting the pressure detection value by each pressure sensor 51, 31' into a voltage value (or current value);
A C is a pressure setting device that sets the appropriate value for injection pressure, AII # A12t A13
tA14 and AXI are servo amplifiers, sO,l ”
'02 + SO5゜SO4 and SX+ are servo pulp, P2 is hydraulic pump s CVl +
CT4 indicates a check valve, RvIIPv2 indicates a relief valve,
These devices are connected as shown in the first figure. In addition,
In the circuit section of FIG. 1, thick lines indicate hydraulic circuits, and thin lines indicate electrical circuits.

Next, the effect will be explained.

First, the resin introduced from the hopper 2 of the injection device 1 is melted and kneaded in the injection cylinder 5 by the rotation of the injection screw 4, and the molten resin is injected into the sprue 14 of the mold 7 by the operation of the injection hydraulic cylinder 6. , distributed from the sprue 14 to each hot runner 16) 16', and each nozzle 17j
17' and nozzle gates 18, 18' into each cavity 30, 30'.

At this time, the resin pressure in each cavity 30930' is individually detected by the pressure sensors 31, 31', and the detection signals are sent to the transducers 'ro, IP, respectively.
O2*'ro31'ro4 is sent to voltage [K
After being converted, amplifiers A011 A021 A03.
, amplified by Ao4 and outputted by arithmetic unit CO29C0
3ICO4 and then arithmetic unit CXI and each servo amplifier A11
s A12 s A13 jA+4 6 Then, the signal sent to the arithmetic unit Cx1 is sent to the servo amplifier Ax1, and this signal is compared with a preset signal from the pressure setting device Px1. Based on this, the spool opening of servo valve SXI is controlled, and hydraulic pump P
2 to the bottom side oil chamber 6a of the injection hydraulic cylinder 6 is controlled, and the injection stroke of the injection screw 4 is controlled, thereby controlling the molten resin at a predetermined injection pressure. It is injected into the mold 7.

On the other hand, during this injection, each of the arithmetic units C01°C0
2#C05IC04 to each servo amplifier Al11A
12+A13+ Signal sent to Al1 and preset pressure setting device of each cavity P01 + PO2
# The signal from “05 +”04 is compared by the servo amplifier, and based on this, each servo pulp S
O1, S02. The spool opening degrees of S05S04 are individually controlled, and each hydraulic cylinder 21y21 is controlled from the hydraulic pump P1.
The flow rate of pressure oil supplied to each hydraulic cylinder is individually controlled.

21. The stroke of 21', that is, the position of each nozzle tip, is individually controlled, and the opening force of the nozzle gates 18, 18' corresponding to each cavity 30°30' is individually controlled, so that the position of each nozzle tip is individually controlled. Molten resin is injected and filled at an appropriate pressure every 50'.

That is, if the first cavity 30 of the four cavities is injected and filled with molten resin, the value detected by the pressure sensor 31 corresponding to that cavity 50 will be one shift corresponding to the predetermined filling pressure. , along with this, the first
Servono (Lube So1 crab is switched to the left position in the drawing,
The oil discharged from the hydraulic pump P1 is supplied to the rond side oil chamber 21a of the hydraulic cylinder 21, and the hydraulic cylinder 21 is operated laterally, and the link 22 is rotated clockwise to move the nozzle tip 20 forward. Nozzle gate 18 force: Closed and the gate opening reaches the minimum value go as shown in Figure 5a.
It is controlled so that This prevents the resin filling pressure force against the first cavity 60 from increasing further, and only the first cavity 60 is switched to injection holding.

On the other hand, the other 2. Fifth. Since the fourth cavities 50' are not yet completely filled with resin, the nozzle tips 20' corresponding to each cavity 50' are in the retracted position, and the gate opening is at its maximum as shown in FIG. Value 1m&X
In this state, the injection screw 4 continues to move forward, and the injection force of the resin continues, and the remaining cavities 30' are injected and filled with resin. Then, in each of the remaining cavities 30', the same control as described above is performed in order from when the filling pressure of the resin injected into the cavity reaches a predetermined filling pressure, and each nozzle tip 20' moves forward. Then, the nozzle gates 18' corresponding to each cavity 50' are sequentially closed.

In this way, all four cavities 30 and 30' are injected and filled with molten resin, and when the filling pressure reaches a predetermined pressure,
Each nozzle tip 20.20' each nozzle gage) 18
．． 18' is closed, the servo valve Sx1 is returned to the neutral position, the supply of pressure oil from the hydraulic pump P2 to the hydraulic cylinder 6 is stopped, the forward movement of the injection screw 4 is stopped, and the injection process is completed. After that, the process is switched to the injection holding process, and in this state, the cooling medium (water or oil) is supplied to each cooling medium supply hole 27, 27', and each cavity 30 is
After the resin filled in the cavities 30 and 30' is cooled and solidified, the mold 7 is opened and the resin molded products cooled and solidified in the cavities 30 and 30' are taken out.

As explained above, according to the present invention, when injecting and filling molten resin into a plurality of cavities provided in a mold from one injection device, the injection filling pressure of the resin is detected for each cavity. Then, based on these detected values, the position of the nozzle tip corresponding to each cavity is individually controlled,
By individually controlling the opening degree of each nozzle gate, resin can be injected and filled in the optimal condition for each cavity. Even if there is a problem, resin can be injected and filled in the optimal condition for each cavity, and high-quality resin molded products can be obtained from all cavities without short slits or overpacking. Also,
It also prevents mold damage caused by overpacking.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing an embodiment of the present invention, Fig. 2 is a sectional view showing an example of a mold, and Figs. , FIG. 4 is a pressure characteristic diagram showing the relationship between injection pressure and resin pressure in each cavity. DESCRIPTION OF SYMBOLS 1... Injection device, 2... Hopper, 5... Injection cylinder, 4... Injection screw, 5... Injection nozzle, 6...
... Hydraulic cylinder for injection, 7... Mold, 8... Fixed plate, 9... Movable plate, 10... Fixed mold, 11.
...Movable mold, 14...Sprue, 16, 16'...
Hot runner, 17.17'...nozzle, 18y18
'... Nozzle gate, 20.20'... Nozzle tip, 21.21'... Hydraulic cylinder, 22.22/.
... Link, 26126' ... Nozzle heater, 30.
30'...Cavity, 31.31'...Pressure sensor N Tol 1 To21 To, + T0
4 ”'Converter, AOl ”02tA (+53 A0
4”・Amplifier, C01) CO2tC06IC04IC
XI"' Arithmetic unit, AIT + AI2+ Al5y
AlAs AXI "" servo amplifier, PO1+
"02t PO35P04* PXl - Pressure setting device % S011 802 + -j'05 +
S04 s ""XI"-servo valve, p,, p2
···Hydraulic pump. Patent applicant Kobe Steel, Ltd. Representative Patent attorney Etsuji Kotani, -,, +,
? 7';, 1. ,i,:,'. ,-”5・□′ 3rd (k))

Claims (1)

[Claims] 1. Molten resin is injected and filled into multiple cavities provided in the mold using an injection device, and the position of each nozzle chip provided in the nozzle gate of each cavity is individually controlled. A method for controlling an injection molding machine, characterized in that the resin pressure in each cavity is individually controlled by individually controlling the opening degree of a nozzle gate.